1. Field of the Invention
The present invention relates to an air conditioner, and, more particularly, to an air conditioner incorporating valve devices for interrupting introduction of refrigerant into one or more indoor units, which are not in use, among a plurality of indoor units, whereby reliability of the air conditioner is improved.
2. Description of the Related Art
Generally, an air conditioner is an apparatus that cools or warms the interior of at least one room to provide a pleasant indoor environment. The air conditioner introduces air from the interior of the at least one room, heats or cools the introduced air, and discharges the heated or cooled air into the interior of the at least one room.
FIG. 1 is a circuit diagram schematically illustrating the structure of a conventional air conditioner.
As shown in FIG. 1, the conventional air conditioner comprises: a compressor 2 for compressing low-temperature and low-pressure gas refrigerant into high-temperature and high-pressure gas refrigerant; an outdoor heat exchanger 4 for performing heat exchange between the high-temperature and high-pressure gas refrigerant discharged from the compressor 2 and outdoor air to condense the high-temperature and high-pressure gas refrigerant into liquid refrigerant while discharging heat; an expansion device 6 for expanding the liquid refrigerant condensed by the outdoor heat exchanger 4 into low-temperature and low-pressure 2-phase refrigerant, which is composed of gas refrigerant and liquid refrigerant, and an indoor heat exchanger 8 for absorbing heat from indoor air to evaporate the low-temperature and low-pressure 2-phase refrigerant introduced from expansion device 6 into gas refrigerant.
The compressor 2 and the outdoor heat exchanger 4 are mounted in an outdoor unit 10, and the indoor heat exchanger 8 and the expansion device 6 are mounted in an indoor unit 20. The indoor unit 20 is connected to the outdoor unit 10 via service valves 22.
The compressor 2 comprises two constant-speed compressors, which are connected to each other via a common accumulator 12.
Specifically, the compressor 2 comprises first and second compressors 14 and 16, and the common accumulator 12 is connected to first and second inlet pipes 24 and 26 provided at the first and second compressors 14 and 16, respectively.
To the first and second compressors 14 and 16 are respectively connected first and second outlet pipes 28 and 30, through which high-temperature and high-pressure gas refrigerant is discharged. On the first and second outlet pipes 28 and 30 are mounted first and second check valves 32 and 34 for preventing the high-temperature and high-pressure gas refrigerant from flowing backward, respectively.
The first and second outlet pipes 28 and 30 are connected to a third outlet pipe 36 for guiding the refrigerant discharged from the compressor 2 to the outdoor heat exchanger 4.
In order to ensure that the pressure at the inlet part of the first compressor 14 is in equilibrium with the pressure at the outlet part of the first compressor 14 when the first compressor 14 is stopped, a first connection pipe 38 is connected between the first inlet pipe 24 and the first outlet pipe 28, and a first cut-off valve 40 is mounted on the first connection pipe 38.
In order to ensure that the pressure at the inlet part of the second compressor 16 is in equilibrium with the pressure at the outlet part of the second compressor 16 when the second compressor 16 is stopped, on the other hand, a second connection pipe 42 is connected between the second inlet pipe 26 and the second outlet pipe 30, and a second cut-off valve 44 is mounted on the second connection pipe 42.
The operation of the conventional air conditioner with the above-stated construction will be described below.
When the first and second compressors 14 and 16 are simultaneously operated, refrigerant compressed by the first and second compressors 14 and 16 is discharged through the first and second outlet pipes 28 and 30, and is then introduced into the outdoor heat exchanger 4 through the third outlet pipe 36.
The outdoor heat exchanger 4 performs heat exchange between the refrigerant introduced into the outdoor heat exchanger 4 and outdoor air such that heat is transferred to the outdoor air to condense the refrigerant introduced into the outdoor heat exchanger 4.
The condensed refrigerant passes through the expansion device 6. As a result, the condensed refrigerant is expanded into low-temperature and low-pressure 2-phase refrigerant. The expanded refrigerant passes through the indoor heat exchanger 8. As a result, the expanded refrigerant absorbs heat from indoor air, and therefore, the expanded refrigerant is evaporated. The evaporated refrigerant is introduced into the first and second compressors 14 and 16 through the common accumulator 12.
When the first compressor 14 is stopped, on the other hand, the first cut-off valve 40 is opened, and therefore, the refrigerant discharged from the first compressor 14 is guided into the first inlet pipe 24 through the first connection pipe 38, and is then introduced into the first compressor 14.
As a result, the first inlet pipe 24 of the first compressor 14 is in equilibrium with the first outlet pipe 28 of the first compressor 14.
In the conventional air conditioner, however, it is not possible to prevent refrigerant from being introduced into the indoor unit 20, since only the expansion device 6 is mounted in the indoor unit 20. Recently, various air conditioners each incorporating a plurality of indoor units have been proposed. In the case that the conventional air conditioner is provided with such a plurality of indoor units, refrigerant is introduced into one or more indoor units, which are not in use, among the plurality of indoor units. As a result, it is difficult to control the capacity of the air conditioner. Also, oil is accumulated in one or more indoor units, which are not in use, and therefore, reliability of the air conditioner is lowered.